As such a kind of driving tool, there is known a tool including a head valve which controls a flow of compressed air into a cylinder. When a trigger of the driving tool is manipulated, the head valve is operated to open a supply passage into the cylinder. Accordingly, the compressed air flows into the cylinder to operate a piston, and thus a fastener is driven. At this time, an exhaust passage communicating with the inside of the cylinder is closed by the head valve. When the driving is completed, and the head valve returns to an initial position, the supply passage into the cylinder is closed, and the exhaust passage communicating with the inside of the cylinder is opened to discharge the compressed air in the cylinder.
In such a structure, it is ideal that the exhaust passage communicating with the inside of the cylinder is closed at the same time when the supply passage into the cylinder is opened. However, it is difficult to perform the operation in a strictly simultaneous manner due to the problem such as dimension management. Therefore, in practice, a structure is adopted in which the exhaust passage is closed after the supply passage is opened or the supply passage is opened after the exhaust passage is closed.
However, in the structure that exhaust passage is closed after the supply passage is opened, there is a timing when the supply passage and the exhaust passage are not sealed, and thus a problem occurs in which the compressed air supplied from the supply passage leaks from the exhaust passage, and an air consumption amount is increased.
On the other hand, in the structure that the supply passage is opened after the exhaust passage is closed, a slide resistance in a seal portion is increased, and thus a problem occurs in which the response of the head valve is delayed to cause an energy loss or a discharge delay.
In Japanese Patent Publication (JP-B) No. 4706604 as a technology relating thereto, the description is given about a technology having a structure that the leg portion extending from the outer circumference of the head bumper has a ring-shaped seal member extending toward the main valve (head valve), and the seal member performs sealing by contacting the inner wall surface of the main valve.
According to such a technology, in the structure that the exhaust passage is closed after the supply passage is opened, the seal member extending toward the head valve is provided so that the timing when the supply passage is opened can be set close to the timing when the exhaust passage is closed and the leakage of the compressed air into the exhaust passage can be suppressed.
In the technology described in JP-B-4706604, however, sealing is performed by contacting the rubber seal portion with the inner wall surface of the head valve, and thus a problem occurs in which it is necessary to severely manage a dimension. That is, there is a concern that the rubber is changed in a dimension by an error in production or a temperature change. When the dimension is changed, a problem occurs in which the slide resistance with the head valve is increased to affect an operation, or conversely, the seal portion is apart from the head valve so that it becomes difficult to secure airtightness.
In this regard, an object of the disclosure is to provide a driving tool, of which a structure that the exhaust passage is closed after the supply passage into a cylinder is opened, and in which it is suppressed that compressed air leaks from an exhaust passage after a supply passage is opened and it is not necessary to severely manage a dimension in producing.